Iron (Fe) is one of most the important nutrients for phytoplankton growth in the ocean, making it a crucial element in the regulation of the ocean carbon balance and biogeochemical cycles. Atmospheric deposition of Fe to the ocean has been increased due to human activities, which can significantly alter the marine ecosystem. These necessitate a comprehensive understanding of how the ocean Fe cycling operates and how it will respond to human perturbations.

Hydrological extremes, including both extreme precipitation events and droughts, have profound impacts on human life, health, and socioeconomic well-being. U.S. hydrological extremes are dynamically connected to large-scale meteorological patterns (LMPs) (e.g., atmospheric blocking events, cutoff-low systems, and cyclones/anticyclones) and planetary-scale climate modes (PCMs) (e.g., El Niño Southern Oscillation and Pacific Decadal Oscillation).

The Atlantic Meridional Overturning Circulation (AMOC) transports warm surface water northward across the equator, carrying heat from the Southern to the Northern Hemisphere. AMOC plays a central role in the global redistribution of heat and precipitation during both abrupt and longerterm climate shifts. Over the next century, AMOC is projected to weaken due to greenhouse gas warming, though the skill of these projections is dependent on a better understanding of how AMOC changes are forced, including the evolving states of its constituent water masses.